1. Technical Field
The present disclosure relates to a multi-port interface circuit and associated power saving method, and more particularly, to a multi-port interface circuit and associated power saving method capable of switching between multiple input ports and effectively saving power consumption without re-identifying content protection.
2. Description of Related Art
A multimedia playback apparatus, e.g., a television (TV), a monitor, an audible apparatus and a display, has an interface circuit for receiving a source apparatus that provides a multimedia data stream. In the modern information society, since the source apparatus becomes diversified, an interface circuit of a modern playback apparatus has a plurality of input ports that are respectively coupled to difference source apparatuses. A user selects one of the input ports to playback by a playback apparatus a data stream in the selected input port. For example, the source apparatus is a satellite, a set-up box (STB) of a wired and/or wireless TV, a hard disk, a memory card and/or a compact disc (CD) player, a game console, an audio-visual (AV) amplifier and/or an equalizer, or an AV capturing apparatus, e.g., a mobile, a digital camera, a digital video recorder, and the like. In order to meet requirements of the diversified source apparatuses, the interface circuit having a plurality of input ports is a basic demand of the modern playback apparatus.
In order to protect the copyright of a multimedia data content production, content protection of a data stream becomes a development trend of the modern multimedia technology. When a data stream is to be transmitted from a source apparatus to a playback apparatus, a mechanism for performing content protection on the data stream between the source apparatus and the playback apparatus is simply described below. A data stream transmitter of the source apparatus identifies with a receiver of the playback apparatus according to a predetermined protocol, and legally transmits the data stream only after it is determined that the transmitter and the receiver are authorized. After the identification, an encryption/decryption parameter (e.g., key information and/or a pseudo random sequence for encryption/decryption) between the transmitter and the receiver is coordinated. According to the encryption/decryption parameter, the transmitter encrypts and transmits AV multimedia content of the data stream to the receiver, and the receiver decrypts content carried in the data stream for playback. Since the data stream between the transmitter and the receiver is encrypted, the content of the data stream cannot be accurately obtained even if the data stream between the transmitter and the receiver is tapped and intercepted to achieve an object of content protection.
Since the data stream extends as time goes by, content protection also needs to be periodically synchronized in the form of a stream. That is, the transmitter and the receiver synchronously periodically update/initialize the encryption/decryption parameter (e.g., the pseudo random sequence for encryption/decryption) according to the parameter coordinated during identification, and periodically exchange identification information to confirm whether the previous identification status is maintained. When either the transmitter or the receiver interrupts synchronization of the content protection, both of them need to spend excessive time in re-identification. In other words, during an extension period of the data stream, the transmitter and the receiver need to maintain content protection synchronization to maintain the identification status.